1. Field of the Invention
The present invention relates to media-based solid-liquid filters, and more particularly to a new and improved sand media filtering device for efficiently and continuously filtering solids from liquids in a liquid/solid mixture for longer periods of time with fewer backwashing operations.
2. Description of the Prior Art
Many agricultural, industrial, and commercial processes and systems require filtration of the water or other fluids used. The ultimate purpose or use for the water or fluid generally dictates the amount of filtration required. For some operations, filtration of particles down to 20 microns is sufficient, while others may require filtration down to 5 microns, 1 micron or even less. To address these needs, different filtration systems have been developed.
Screen or wire mesh filters are well known in the art. Such filters typically employ one or more layers of woven wire screen or mesh, sometimes having different opening sizes. Water or fluid is passed through the mesh which filters out particles larger than the smallest opening sizes of the mesh. Because of their permanent fixation, such filters can become easily and quickly clogged, and therefore require constant cleaning or backwashing. This kind of constant interruption of the filtration process cannot be tolerated in many environments.
Media-based filters have also been developed which include one or more layers of different sized media (such as sand or gravel) deployed in a filtration chamber. Water or fluid is passed through the chamber, and the media filters out particles. The media may range in size from coarse to fine, depending upon the amount of filtration required, and may include activated carbon to remove organic materials such as bacteria and the like. Filtered particles accumulate in the media and must eventually be removed by backwashing.
For many media-based filters, it is common to backwash three or four times per day. This causes a disruption in the filtering process, and often requires use of filtered water or fluid to perform the backwashing operation itself. It is possible to lengthen the time between backwashing operations by providing larger filters with more media, however large filters may not be appropriate or affordable in many applications. Unfortunately, media-based filtration systems also suffer from a significant drawback posed by the potential for agglomeration or caking of filtered particles at the top of the media bed, forming a solid layer. When such caking occurs, it may slow or stop the filtration process until the caked material can be backwashed out. More significantly, if the caked material becomes too thick, it may also interrupt or prevent the backwashing process itself.
It is therefore desirable to provide a media-based fluid filtration system that is capable of providing filtration for longer periods of time between backwashes without increasing the size of the system, and which prevents the agglomeration of filtered particles at the top of the media bed.